Intervertebral fusion implant

ABSTRACT

The present invention provides an intervertebral implant for implantation in a treated area of an intervertebral space between vertebral bodies of a spine. The implant includes a spacer portion having an inferior and superior surface, wherein the inferior and superior surfaces each have a contact area capable of engaging with anatomy in the treated area, and the inferior and superior surfaces define a through-hole extending through the spacer body. The present invention further provides screw holes extending from a side portion to the inferior and superior surfaces of the spacer portion and a plate portion rigidly coupled to the spacer portion through a coupling means, wherein the plate portion contains screws holes for receiving screws. A screw back out prevention mechanism adapted on the plate portion and prevents the back out of screws from the screw holes.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of patentapplication Ser. No. 12/202,690 filed on Sep. 2, 2008 now U.S. Pat. No.8,328,872, which is incorporated by its entirety herein.

FIELD OF THE INVENTION

The present disclosure generally relates to a fixation device forpositioning and immobilizing at least two adjacent vertebra. Inparticular, the present invention relates to a stand alone interbodyfusion device for implementation in the spine.

BACKGROUND OF THE INVENTION

The vertebral spine is the axis of the skeleton on which all of the bodyparts “hang”. In humans, the normal spine has seven cervical, twelvethoracic and five lumbar segments. The lumbar spine sits upon thesacrum, which then attaches to the pelvis, and in turn is supported bythe hip and leg bones. The bony vertebral bodies of the spine areseparated by intervertebral discs, which act as joints but allow knowndegrees of flexion, extension, lateral bending, and axial rotation andtranslation.

The typical vertebra has a thick anterior bone mass called the vertebralbody, with a neural (vertebral) arch that arises from the posteriorsurface of the vertebral body. The central of adjacent vertebrae aresupported by intervertebral discs. The spinal disc and/or vertebralbodies may be displaced or damaged due to trauma, disease, degenerativedefects, or wear over an extended period of time. One result of thisdisplacement or damage to a spinal disc or vertebral body may be chronicback pain. In many cases, to alleviate back pain from degenerated ofherniated discs, the disc is removed along with all or part of at leastone neighboring vertebrae and is replaced by an implant that promotesfusion of the remaining bony anatomy.

However, the success or failure of spinal fusion may depend upon severalfactors. For instance the spacer or implant or cage used to fill thespace left by the removed disc and bony anatomy must be sufficientlystrong to support the spine under a wide range of loading conditions.The spacer should also be configured so that it likely to remain inplace once it has been positioned in the spine by the surgeon.Additionally the material used for the spacer should be biocompatiblematerial and should have a configured that promotes bony ingrowth.

In combination with spacers or cages, a plating system is used tofurther stabilize the spine during the fusion process. These devices,commonly referred to as bone fixation plating systems, typically includeone or more plates and screws for aligning and holding vertebrae in afixed position with respect to one another. Plating systems independentof the spacers provide additional complications such as loosening andfailure of the hardware. Two common failures are the breakage of theplates, and the backing out of screws into soft tissues of the patient'sbody. The backing out of the screws is typically a result of the screwsfailure to achieve a sufficient purchase in the bone, although thestripping of the screws has also been known to cause this problem.Another common problems is that plating systems require “carpentry” workto match fit aspects of the vertebral bodies.

There is a need for a spine stabilization system that in promotes fusionof adjacent vertebrae while at the same time provides stabilization ofthe spinal area where fusion occurs. There is a need for a system thatincorporates both the fusion element and the plating element in onesystem to reduce the possible complications that may occur. There isalso a need to provide a system that reduces the complications that mayoccur in the fusion element and the plating element and a need for thissystem to be configured so that positioning this system is efficient andeasy.

SUMMARY OF THE INVENTION

The present invention provides an intervertebral implant forimplantation in a treated area of an intervertebral space betweenvertebral bodies of a spine. The implant includes a spacer portionhaving an inferior and superior surface, wherein the inferior andsuperior surfaces each have a contact area capable of engaging withanatomy in the treated area, and the inferior and superior surfacesdefine a through-hole extending through the spacer body. The presentinvention further provides screw holes extending from a side portion tothe inferior and superior surfaces of the spacer portion and a plateportion rigidly coupled to the spacer portion through a coupling means,wherein the plate portion contains screws holes for receiving screws. Ascrew back out prevention mechanism is adapted on the plate portion andprevents the back out of screws from the screw holes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of an intervertebralimplant according to the present invention;

FIG. 2 is another perspective view of the embodiment of the implantshown in FIG. 1;

FIG. 3 is a side view of the intervertebral implant of FIG. 1;

FIG. 4 is a top view of the intervertebral implant of FIG. 1;

FIG. 5 is an exploded view of the intervertebral implant of FIG. 1;

FIGS. 6 and 7 is a perspective view of the intervertebral implant ofFIG. 1 which include illustrations of bone fasteners;

FIG. 8 is another side view of the intervertebral implant of FIG. 1incorporating bone fasteners;

FIG. 9 is a perspective view of another embodiment of the intervertebralimplant;

FIG. 10 is a front view of the intervertebral implant with bone screwslocked of FIG. 9;

FIG. 11 is a front view of the intervertebral implant illustrated inFIG. 9;

FIG. 12 is an exploded view of the intervertebral implant with bonefasteners unlocked of FIG. 9;

FIG. 13 is yet another embodiment of the intervertebral implant;

FIG. 14-16 are different views of the intervertebral implant of FIG. 13;and

FIG. 17 is an exploded view of the intervertebral implant of FIG. 14according to the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Embodiments of the disclosure are generally directed to flexiblestabilization systems for use with the anterior, antero-lateral,lateral, and/or posterior portions of at least one motion segment unitof the spine. The systems of the invention are designed to beconformable to the spinal anatomy, so as to be generally less intrusiveto surrounding tissue and vasculature than existing rigid stabilizationsystems.

Certain embodiments may be used on the cervical, thoracic, lumbar,and/or sacral segments of the spine. For example, the size and massincrease of the vertebrae in the spine from the cervical to the lumbarportions is directly related to an increased capacity for supportinglarger loads. This increase in load bearing capacity, however, isparalleled by a decrease in flexibility and an increase insusceptibility to strain. When rigid immobilization systems are used inthe lumbar segment, the flexibility is decreased even further beyond thenatural motion restriction of that segment. Replacing the conventionalrigid immobilization systems with certain embodiments disclosed hereinmay generally restore a more natural movement and provide added supportto the strain-susceptible area.

FIGS. 1-8 illustrate the different views of one particular embodiment ofthe present invention. The intervertebral fusion implant as shown inFIGS. 1-8 is a stand-alone anterior lumbar interbody fusion device usedto provide structural stability in skeletally mature individualsfollowing discectomies. These implants are available in various heightsand geometric options to fit the anatomically needs of a wide variety ofpatients. Specifically, FIGS. 1-4 illustrate one embodiment of anintervertebral fusion implant 10 according to the present invention.Implant 10 is generally positioned in the intervertebral space betweentwo adjacent vertebrae. As shown in the figures, implant 10 primarilyincorporates a spacer portion 12 and a plate portion 14. In thisparticular embodiment, the spacer portion 12 includes a graft window 16for the placement of bone graft to enhance fusion between two adjacentvertebrae. The plate portion 14 includes at least one screw hole 18,however, in the preferred embodiment of the present invention, threescrew holes 18 are provided. Also, in the plate portion 14 of theimplant 10, a screw back out prevention mechanism 20 is provided. Thereis also provided a coupling means 26 which connect the spacer portion 12and the plate portion 14 rigidly to each other. The coupling means 26will be discussed in greater detail with reference to FIGS. 5-8.

The spacer portion 12 can be comprised of any material that is conduciveto the enhancement of fusion between the two adjacent vertebrae. In oneparticular embodiment, the spacer portion 12 is made of PEEK materialwhich is physiologically compatible. It should be noted that any othermaterial that are physiologically compatible may also be used. Thespacer portion 12 contains tantalum pins that enable radiographicvisualization. The spacer portion 12 further comprises superior andinferior portions that are provided with a plurality of pyramidalprotrusions 13. The superior and inferior portions of the spacer portionare bi-convex for greater contact with the vertebral endplates of theadjacent vertebrae. The protrusions 13 can be configured to be any sizeor shape for further anchoring the spacer portion 12 to each of theadjacent vertebrae. Protrusions 13 on the superior and inferior surfacesof each implant grip the endplates of the adjacent vertebrae to aid inexpulsion resistance.

The plate portion 14 can also be comprised of any physiologicallycompatible material. In the preferred embodiment, the plate portion ofthe implant 10 is composed of titanium. The plate portion 14 asillustrated in FIG. 1, are provided with three screw holes. However, itshould be noted that implant 10 may be comprised of only one screw hole.The screw holes 18 are situated both in the spacer portion 12 and theplate portion 14 for receiving bone screws which are attached to theadjacent vertebral bodies at different angles.

FIG. 5 illustrates an exploded view of the intervertebral stand alongfusion device 10. In this exploded view, clearer view of the combinationof the plate portion 14 and the spacer portion 12 is illustrated. Thespacer portion 12 and the plate portion 14 are coupled to each otherview connection points 24 and through the use of connection pins 26 and28.

FIGS. 6-8 illustrate the fusion device 10 in various views associatedwith the screws 30 provided in screw holes 18. The screw holes 18 areconfigured to receive screws 30 at various angles. The screws 30 enterthe screw holes 18 at specified angles to enter the adjacent vertebralbodies at the optimal locations. The screws 30 are configured andadapted to provide optimal purchase with the adjacent vertebral bodies.

Now, turning to the method of positioning the implant, it should benoted that the intervertebral implant 10 is positioned in the spineafter the disc portion between two vertebral bodies is exposed andremoved using rongeurs and other suitable instruments. The posterior andlateral walls of the annulus are generally preserved to provideperipheral support for the implant and graft materials. A trial deviceattached to a trial holder is then inserted into the disc space todetermine size of the implant. This procedure is generally conductedusing fluoroscopy and tactile feel. After the appropriate sized implantis selected and attached to an implant holder and drill guide, theimplant may be inserted into the disc space. Once the implant ispositioned with the disc space, supplemental graft material can used toenhance fusion. Once the implant is positioned inside the disc, an awlor any similar type of instrument can be used to drill through the screwhole and break the cortex of the adjacent vertebral body. The surgeonperforming this procedure may then use a depth gauge to determine thescrew length. Once the appropriate screw length is determined, screwsare inserted using a self-retaining screwdriver. After the screws arefinally inserted and secured thereby providing solid purchase with theadjacent vertebral bodies, the screw anti-back out mechanism is engagedand secured. In this particular embodiment, the anti-back out mechanismis two set screws that retain the three screws with the implant. Itshould be noted that the implant may be implanted in the vertebral spaceusing an anterior, posterior and/or lateral approach.

FIG. 9 illustrates a perspective view of the zero-profile intervertebralimplant 32 for positioning in the cervical region of the spine. Thepresent invention relates to an implant having a peek spacer portion 33that is coupled to a titanium plate portion 34 through the use oftitanium dowel pins 39. However, it should be noted that the titaniumplate portion 34 and the peek spacer portion 33 maybe coupled throughany other feasible means such as hooks, screws, and any other type offastening means. The implant 32 also allows for at least two titaniumscrews 36 and 37 to be inserted at a compound angle for maximum screwpurchase into the superior and inferior vertebral bodies. A lockingmechanism 38 is provided on the plate portion 34 to capture the sides ofboth of the at least two screws 36 and 37 with a 90 degree turnpreventing the titanium screws 36 and 37 from backing out. It should benoted that the present application is not limited to being of a PEEKspacer and a titanium plate. Other materials that are physiologicallycompatible which are similar and which may be unique to spacers andplates may be utilized in various combinations.

FIGS. 10 and 11 illustrate the front view of the plate portion of theimplant. Specifically, FIGS. 10 and 11 illustrate a closed and an openposition respectively with reference to the anti-back out mechanism 38.Also, it should be noted that the titanium plate 34 is provided withknife like edges 35 which are designed to engage the vertebral body andprovides additional torsional stability to that of the bone screws. Theplate 35 is also provided with “eye brow” like structure which fullycaptures the bone screws 36 and 37 while still allowing for the screwsto reside about the tooth root plane and remaining lower than the tooth(protrusions on the spacer portion 33). The plate 35 geometry allows forthe minimum reduction of peek volume. The plate 35 height remains levelto the peek tooth root so that compressive loads are always subjected tothe peek body where the graft is contained. Compound holes are drilledto accept bone screws 36 and 37 and to allow for fixed or variable anglescrews. The anti-back out mechanism is engaged so that the screws 26 and37 do not back out of the implant 32.

FIG. 12 illustrates an exploded view of the intervertebral implant. Theplate portion 34 and spacer portion 33 have at least 2 male and femaleledges which are capable of interfacing with each other. The connectionof the male and female ledges are offset at different heights tominimize cross-sectional area loss. Also illustrated in FIG. 12 is thedowel pins used to connect the spacer portion to the plate portion asone means of coupling of the spacer portion 33 and the plate portion 34.It should be noted that various means such as hooks, staples and screwscan be used to attach the spacer portion to the plate portion of thepresent invention.

The spacer portion 33 of the implant provides a leading edge chamferwhich enables self distraction of the vertebral bodies while inserting.The spacer portion 33 also provides teeth like structures in thesuperior and inferior aspects of the spacer body to help preventmigration of the implant. The root of the teeth or protrusions on thebase of the implant serves as the defining plane for the superior andinferior vertebral bodies. Finally, the spacer portion 33 provides anaxial shaped hole which enables a maximum amount of graft for packingwithin the implant. However, it should be noted that the graft hole canbe designed to be multiple holes or any in other geometrical shape toenhance fusion through the insertion of graft material.

FIGS. 13-16 illustrate an intervertebral implant for positioning in theintervertebral space using a lateral approach. The intervertebralimplant 40 consists of a spacer portion 42 and a plate potion 44. Thespacer portion and the plate portion are configured to be able toreceive screws 46 and 48 for attachment to adjacent vertebral bodies.The spacer portion 42 and the plate portion 44 are rigidly coupledtogether through a coupling means 52. The plate portion 44 is providedwith an anti-back out mechanism 50 so that the screws 46 and 48 arefixedly retained within the fusion device 40.

FIG. 17 illustrates another embodiment of an intervertebral implant 60that is positioned into the disc space laterally. In this embodiment,which is similar to the embodiment disclosed in FIGS. 13-16, the spacerportion 62 is provided with a plurality of protrusions in the superiorand inferior portions. These protrusions grip the endplates of theadjacent vertebrae to aid in expulsion resistance. The spacer portion 62also contains a plate receiving area 63 for receiving the plate portion64. The plate receiving area 63 is configured to receive a plateprotrusion 66 for coupling the spacer portion 62 and the plate portion64 together through the use of pins or any other similar type ofcoupling means. The spacer portion 62 and the plate portion 64 arerigidly coupled together through the use of the coupling means.

The plate portion 64 is configured with at least two screw holes forreceiving screws 68. The screws 68 are positioned at angles to insertthrough the spacer and the adjacent vertebral body to gain maximumpurchase and stability. The screws 68 are retained with the implant 60through the use of an anti-screw back out mechanism 70. When thismechanism is engaged by turning at least 90 degrees through the use aninstrument such as a screwdriver, the screws 68 are maintained withinthe implant and the honey structure of the adjacent vertebral bodies.

While it is apparent that the invention disclosed herein is wellcalculated to fulfill the objects stated above, it will be appreciatedthat numerous modifications and embodiments may be devised by thoseskilled in the art.

What is claimed is:
 1. An intervertebral implant for implantation in atreated area of an intervertebral space between vertebral bodies of aspine, wherein said implant comprises: a spacer portion having aninferior and a superior surface, an anterior surface, posterior surface,and first and second sides, wherein the inferior and superior surfaceseach have a contact area capable of engaging with anatomy in the treatedarea, and the inferior and superior surfaces define a through-holeextending through the spacer portion; at least a first hole extendingfrom the anterior surface to the superior surface of the spacer portionand at least a second hole extending from the anterior surface to theinferior surface of the spacer portion; a plate portion rigidly coupledto the spacer portion through a coupling mechanism, wherein the plateportion contains at least first and second holes extending from ananterior surface of the plate to a posterior surface of the plate, theat least first and second holes configured for receiving fasteners; andwherein a fastener back out prevention mechanism is adapted on the plateportion and prevents the back out of the fasteners from the first andsecond holes, wherein the spacer portion length from the anteriorsurface to the posterior surface is greater than a distance from a firstside to a second side of the plate portion, wherein a width of thespacer portion from the first side to the second side is greater thanthe width of the plate portion, wherein the spacer portion and the plateportion are configured to be positioned laterally wherein thethrough-hole extending through the spacer portion from the inferiorsurface to the superior surface is configured with a length extendingfrom the anterior surface of the spacer portion towards the posteriorsurface of the spacer portion, wherein the length of the through-hole isgreater than the width of the plate portion wherein the plate portion isconfigured with no more than the first and second holes, wherein theplate portion further includes extensions with no openings and whereinthe extensions are generally flush with the anterior surface of theplate.
 2. The intervertebral implant of claim 1, wherein the fastenersare inserted into adjacent vertebral bodies at divergent angles.
 3. Theintervertebral implant of claim 1, wherein the coupling mechanism is atleast one pin that rigidly couples the spacer portion with the plateportion.
 4. The intervertebral implant of claim 1, wherein the plateportion and the spacer portion are configured to structurally mate withone another.
 5. The intervertebral implant of claim 1, wherein the plateportion is configured to be substantially flush with the vertebral body.6. The intervertebral implant of claim 1, wherein the plate portion iscomprised of metal.
 7. The intervertebral implant of claim 6, whereinthe metal is comprised of titanium.
 8. The intervertebral implant ofclaim 1, wherein the spacer portion is comprised of plastic.
 9. Theintervertebral implant of claim 1, wherein the spacer portion comprisesa plurality of protrusions on superior and inferior portions.
 10. Amethod of implanting an intervertebral implant for implantation in atreated area of an intervertebral space between vertebral bodies of aspine, wherein said implant comprises: accessing the intervertebralspace from a lateral approach; removing a disc portion with instrumentsadapted to be used in a lateral approach to the vertebral space;positioning the intervertebral implant within the intervertebral space,wherein the intervertebral implant comprises: a spacer portioncomprising an inferior and superior surface, an anterior and posteriorsurface, and first and second sides, wherein the inferior and superiorsurfaces each have a contact area capable of engaging with anatomy inthe treated area, and the inferior and superior surfaces define athrough-hole extending through the spacer body; a first and secondthrough hole extending from an anterior surface of the spacer portion tothe inferior and superior surfaces of the spacer portion; a plateportion rigidly coupled to the spacer portion, wherein the plate portioncontains a first and second through hole for receiving a first andsecond fastener; and a fastener back out prevention mechanism adapted onthe plate portion and prevents the back out of the first and secondfastener from the first and second through hole, wherein the spacerportion has a length from the anterior surface to the posterior surfacethat is greater than a distance from a first side of the plate portionto a second side of the plate portion and the plate portion is providedwith torsional stabilizers, the torsional stabilizers configured with noopenings, wherein width of the spacer portion from the first side to asecond side is greater than the distance from the first side of theplate portion to the second side of the plate portion placing a firstand second fastener into the first and second through hole and engagingthe adjacent vertebral bodies with the first and second fasteners; andengaging and locking the fastener back out prevention mechanism toprevent the first and second fasteners from backing out of theintervertebral implant wherein the spacer portion and the plate portionare configured to be positioned laterally wherein the through-holeextending through the spacer portion from the inferior surface to thesuperior surface is configured with a length extending from the anteriorsurface of the spacer portion towards the posterior surface of thespacer portion, wherein the length of the through-hole is greater thanthe distance from the first side of the plate portion to the second sideof the plate portion, wherein the plate portion is configured with nomore than the first and second through hole for receiving a first andsecond fastener wherein the torsional stabilizers are generally flushwith the anterior surface of the plate.
 11. An intervertebral implantcomprising: a spacer having an upper surface, a lower surface, a firstsides surface, a second side surface, an anterior surface, and aposterior surface, wherein the upper and lower surfaces each have acontact area capable of engaging with adjacent vertebral bodies, andwherein the spacer includes a through-hole extending from the uppersurface to the lower surface of the spacer, a plate having an anteriorsurface, a posterior surface, a first side, a second side, a uppersurface and a lower surface, the plate configured to be coupled to thespacer by a coupling mechanism, the plate includes a first through holeand a second through hole that extends from an anterior surface of theplate to the posterior surface of the plate, wherein spacer includes afirst through hole extending from the anterior surface to the uppersurface of the spacer and a second through hole extending from theanterior surface to the lower surface of the spacer, wherein the plateincludes extensions on the upper and lower surfaces that have noopenings, wherein the first and second through holes of the plate andthe spacer are configured to receive fasteners, wherein a fastener backout prevention mechanism is adapted on the plate for preventing the backout of the fasteners from the first and second through holes of theplate. wherein the spacer length defined from the anterior surface tothe posterior surface is greater than a distance from the first side ofthe plate to the second side of the plate, wherein a width of the spacerfrom the first side to the second side is greater than the distance fromthe first side of the plate to the second side of the plate, wherein thespacer and the plate are configured to be positioned laterally whereinthe through-hole extending through the spacer from the upper surface tothe lower surface is configured with a length extending from theanterior surface of the spacer towards the posterior surface of thespacer, wherein the length of the through-hole is greater than adistance from the first side of the plate to the second side of theplate wherein the extensions are generally flush with the anteriorsurface of the plate.